Theoretical model of hydraulic conductivity for frozen saline/non-saline soil based on freezing characteristic curve

The hydraulic conductivity of frozen soil has significant effects on the moisture and solute migration and on the ice segregation in frost heave when the soil is being frozen. In this study, in accordance with the thermodynamic theory of unfrozen water film, the variation of chemical potential energy of water film due to salt and soil particles is considered. It is highlighted that moisture migration in the frozen soil can be considered as the Darcy flow under a new equivalent water pressure control. On that basis, the expression of pore water freezing temperature and pore radius is yielded, and then the capillary bundle theory and the soil frozen characteristic curve (SFCC) are used for the frozen soil to build a theoretical model to predict the hydraulic conductivity of frozen saline/non-saline soil. Through the comparison of four empirical equations and experimental data, the results achieved using our theoretical model can help to predict the hydraulic conductivity of the frozen soil. Furthermore, frozen non-saline soil achieves 12.47% the contribution of unfrozen water film to hydraulic conductivity, and frozen saline soil achieves 11.25% according to warm frozen soil from 0 to - 2 degrees C. Thus, this important channel cannot be ignored for water migration. Actually, this theoretical model gives an important parameter to the numerical simulation of frost heave in cold regions engineering, which can be referenced for the study on hydraulic conductivity of frozen saline/non-saline soil.